3 Surface-enhanced Raman Scattering ...
39
SERS spectra. Another example that confirms sensitivity of the SERS spectra to
chirality is recognition of phenylalanine enantiomers by the enantiomeric cysteine
monolayer deposited on a silver support [86] and SERS evidence for chiral discrimination in intermolecular interactions between adsorbed methionine molecules [87].
Further exploration of the stereospecificity of SERS may open new possibilities of
applications of SERS spectroscopy in optical sensors of chiral biomolecules.
tERS is a very helpful technique in investigating molecules of biological importance. In 2009, first tERS spectra of cystine adsorbed on ultrasmooth gold substrate
were reported. they indicated local variations of cystine adsorption [88]. It was also
possible to observe two differently protonated histidine forms and determine two
different geometries of adsorption on an atomically flat silver substrate [89]. SERS
data for simple amino acids made it possible to interpret the SERS spectra of more
complex systems such as peptides [90–95], dipeptides [96, 97], and proteins [98–
100]. For example, it was possible to predict major features of the SERS spectra of
penetratin, a 19 amino acid cell penetrating peptide, based on the SERS spectra of
aromatic aminoacids such as tryptophan and phenylalanine and cysteine-containing
aromatic peptides bound to Au nanoshells [91]. As may be seen in Fig. 3.5, the
SERS spectrum of penetratin is dominated by features characteristic of the aromatic
amino acids, greatly simplifying its interpretation.
While interpreting complex SERS spectra of peptides and proteins, it must be
kept in mind that the most strongly enhanced bands in the spectrum correspond to
the vibrational modes involving part of the molecule in the vicinity of the metal
Fig. 3.5 Comparison of empirically predicted ( red) and measured ( black) spectra of penetratin. (a)
molecular model of penetratin, including one phenylalanine ( purple) and two tryptophan ( green).
(b) Raman spectra (peaks assigned to tryptophan are denoted with an asterisk). (c) SERS spectra.
(Reproduced from Ref. [91] with kind permission of the American Chemical Society. Copyright
2008, American Chemical Society)
39
SERS spectra. Another example that confirms sensitivity of the SERS spectra to
chirality is recognition of phenylalanine enantiomers by the enantiomeric cysteine
monolayer deposited on a silver support [86] and SERS evidence for chiral discrimination in intermolecular interactions between adsorbed methionine molecules [87].
Further exploration of the stereospecificity of SERS may open new possibilities of
applications of SERS spectroscopy in optical sensors of chiral biomolecules.
tERS is a very helpful technique in investigating molecules of biological importance. In 2009, first tERS spectra of cystine adsorbed on ultrasmooth gold substrate
were reported. they indicated local variations of cystine adsorption [88]. It was also
possible to observe two differently protonated histidine forms and determine two
different geometries of adsorption on an atomically flat silver substrate [89]. SERS
data for simple amino acids made it possible to interpret the SERS spectra of more
complex systems such as peptides [90–95], dipeptides [96, 97], and proteins [98–
100]. For example, it was possible to predict major features of the SERS spectra of
penetratin, a 19 amino acid cell penetrating peptide, based on the SERS spectra of
aromatic aminoacids such as tryptophan and phenylalanine and cysteine-containing
aromatic peptides bound to Au nanoshells [91]. As may be seen in Fig. 3.5, the
SERS spectrum of penetratin is dominated by features characteristic of the aromatic
amino acids, greatly simplifying its interpretation.
While interpreting complex SERS spectra of peptides and proteins, it must be
kept in mind that the most strongly enhanced bands in the spectrum correspond to
the vibrational modes involving part of the molecule in the vicinity of the metal
Fig. 3.5 Comparison of empirically predicted ( red) and measured ( black) spectra of penetratin. (a)
molecular model of penetratin, including one phenylalanine ( purple) and two tryptophan ( green).
(b) Raman spectra (peaks assigned to tryptophan are denoted with an asterisk). (c) SERS spectra.
(Reproduced from Ref. [91] with kind permission of the American Chemical Society. Copyright
2008, American Chemical Society)